1. Field of the Invention
This invention relates to a gas spring to be used for opening and closing of a rear door of a four-wheel drive or vehicle, which includes vans, station wagons and other type of vehicles.
2. Description of Related Art
In the vehicle, generally there is provided a rear door (an opening and closing member) which is pivoted around a horizontal axis or a perpendicular axis next to vehicle body (main body), with a gas spring provided between the rear door and the body so that the force required for opening the rear door is reduced by a repulsive force (assisting force) of the gas spring.
Among such types of gas springs, there is one, as disclosed by the Japanese Utility Model Application Laid-open Publication No. 63-80346, where the rear door is connected to the body pivotally around a horizontal axis, and a guide pin is provided in a cylinder of the gas spring, and a guide cylinder is extended to cover the cylinder from the both-sides and is disposed in a rod, a guide groove is extended in a direction of extension and compression stroke of the gas spring and is formed in the guide cylinder, and the guide pin is engaged with an engagement stage of the guide groove, to thereby restrict the extension stroke of the gas spring so as to adjust the extent of opening of the rear door in two stages.
According to the gas spring described in the above publication, however, it is necessary to provide the guide pin and the guide cylinder, which results in an increase in the number of parts and an increase in the number of assembly process as well as the cost to manufacture.